The present invention relates to a suction control device designed to be fitted on the end of the handpiece of a lens extraction apparatus employed in ophthalmic surgery.
The general field of application of the invention is those cases where, during a surgical intervention, debris or liquids, in general organic, are to be suctioned from a cavity filled with fluid, for example the anterior chamber of the eye, and with greater safety, by means of strictly limiting all the effects and consequences of uncontrollable or poorly controlled suction.
All the lens extraction apparatuses currently available on the market are fitted with a suction pump connected via flexible lines to a handpiece which may be provided with an ultrasound transducer, said handpiece being maneuvered by the surgeon during the operation. The common feature of all these apparatuses is that the active end of the handpiece intended to penetrate the anterior chamber of the eye, so that ultrasound vibration triggers fragmentation of a body to be removed from the eye, includes only one suction orifice. It is very often found, during use, that when organic debris is being suctioned, obstruction of this single orifice, by a piece of debris, can have serious disadvantages.
The reason is that upon total obstruction or almost total obstruction of this single orifice, the suction pump, irrespective of the type used, continues to provide an underpressure, from its functional part to as far as the active end of the handpiece, the site of the obstruction. As the underpressure is maintained, a negative pressure thus prevails in the cavity formed by the line connecting the pump to the handpiece.
If the debris is finally suctioned, there is then a transitory uncontrolled phenomenon. The suction, on account of the abrupt removal of the obstruction, is amplified, firstly by the potential negative pressure of the column of liquid, present between the end of the handpiece and the pump, secondly, by the return of the walls of the line to the initial position, which walls, being slightly elastic, have caused a reduction in the volume of the column of liquid, and this because they are subjected to the action of the atmospheric pressure during the obstruction and to the underpressure caused by the pump.
Thus, when the active end of the handpiece is placed during the intervention in proximity to a thin organic membrane, such as the posterior capsule of the crystalline lens or the hyaloid membrane, this membrane is irrevocably and violently suctioned, the immediate consequence being its perforation by cutting against the active end of the handpiece. If an organ such as the iris is involved, this is also suctioned, with traumatic consequences. The size of the volume which has been violently suctioned in an unpredicted manner may empty the cavity of the anterior chamber of the eye, which, given the small volume of this cavity, can have serious consequences.
Various means such as calibrated or servo-controlled flaps or valves, electromechanical or electronic control devices connected to pressure sensors or flowrate sensors with a view to controlling the suction pump, prove to be ineffective in solving the existing problems. This is due, firstly, to the speed and suddenness of the transitory phenomena, secondly, to the inertia of the pump, thirdly, to the inertia of the column of liquid, fourthly, to the low values of the liquid volumes present, and, fifthly, to the very short distances, which are surgically necessary, separating the elements present.
It must also be noted that the value of the volume of the cavity of the anterior chamber of the eye is very much lower than the value of the volume existing between the active end of the handpiece and the suction pump. In the configuration presently employed in ophthalmic surgery, the active end of the handpiece is surrounded, over the greater part of its length, by a cylindroconical sleeve which is arranged concentrically, and provided with radial side orifices in its conical end part in proximity to the active end of the handpiece. Thus, there is an annular space between these two pieces since the internal diameter of the sleeve is greater than the external diameter of the active end of the handpiece, and this annular space is employed for infusion of a liquid whose dual role is to cool the active end driven by ultrasound oscillations, and also to replace the volume of suctioned liquid in order to keep the whole anterior chamber of the eye in its normal configuration, while maintaining its internal volume.
During the infusion of this liquid, which can be performed by gravity or by pumping, the inertia of the column of liquid, present between the infusion reservoir or pump and the radial outlets at the conical end of the sleeve, does not permit total and real-time replacement of the volume suctioned in the event of uncontrollable or inadequately controlled suctioning. The result of this is that despite this infusion, the problems set out above still remain. These phenomena, described here, are extreme in form, but there are also more subtle forms of these. There are in fact sub-occlusions, or occlusions of minimal duration, which occur during emulsification of organic fragments, and the transitory phenomena created by these sub-occlusions are responsible for numerous small pressure surges, which, although not having the serious nature of the extreme form of phenomena mentioned above, have harmful consequences for the eye which is being operated on; miosis, inflammation, etc.